"Tangents"
This story was written by Greg Bear, and was first published in Omni in January 1986. Pal Tremont, a Korean boy who likes classical music, is adopted by an American family and comes into the life of Peter Tuthy and writer Lauren Davies. Peter is a mathematician and computer hacker (seemingly based in part on Alan Turing) who is very interested in 4-dimensional space (4-D). Lauren wants Pal to help her with her writings, but Pal is more useful to Peter as he can easily visualize 4-D space. Pal is able to see a whole new world, inhabited by 4-D beings and is even able to play 4-D music for them. The beings eventually make contact and take Pal and Peter into their own world.
Read more about this topic: Hackers (anthology)